Automatic vehicle guidance (i.e., auto-guidance) systems have been used to guide equipment (e.g., vehicles) over a desired path. Such auto-guidance systems are increasingly used for controlling many different types of agricultural and other similar equipment where following a previously defined route is desirable. This allows more precise control of the vehicles than is typically realized if the vehicle is steered by a human.
However, it may sometimes be necessary to wrest control of the vehicle from the auto-guidance system (e.g., in case of emergency or obstacle). In such cases, auto-guidance and steering systems must be capable of detecting an operator's request for control of the vehicle. Various methods and apparatus exist for detecting such a request.
Currently, in some cases, a pressure sensor is placed on the hydraulic steering load-sense line of the vehicle. The pressure sensor detects a change in pressure as the operator turns a steering wheel. The pressure change is transmitted as an electrical signal to a steering controller, which disables the auto-steering functions of the auto-guidance system.
This method is deficient in that pressure spikes and/or drops may be caused on the steering load-sense line by outside influence (e.g., changes in the work environment, pressure variations, etc.). These pressure variations may be misinterpreted by the pressure sensor as an attempt to gain manual control of the vehicle. This false detection can prematurely shut down the auto-steering system.
In other cases, a manual steering system that is stronger than the auto-steering system is used. When the operator engages the steering wheel, the stronger manual steering system will overpower the auto-steering system and allow the operator to steer the vehicle off the intended auto-guidance course. If the operator steers the vehicle sufficiently off course (as determined by a Global Positioning System (GPS) unit, control parameters, etc.), the auto-guidance system will disengage the auto-steering function.
This method is deficient in that the operator must fight the auto-steering system until the vehicle is sufficiently off course. The amount of effort, time, and distance off course required to precipitate a disengagement of the auto-steering function varies according to control parameters, but may be significant.
Therefore, alternative components and methods are required to detect operator input and invoke shutdown of the auto-steering function of auto-guidance systems.